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in the slot marked 100 feet. and when the subiect
is about 8 feet from the lens. set the indicatoi in
the slot marked 8 feet. When the subiect is close
to the lens, then use a Kodak Portrait Attachment,
seepage 35, or use a small stop opening, see table
below.What Depth of Focus Means
Suppose that the lens is used at its full opening,
U.S. 4, and the focus is set at eight feet, an object
eight feet distant will be sharp, but objects seven
and ten feet distant will not be sharp. Stop the
lens down to U.S. 16 and those objects each side of
the exact point of focus will increase in sharpness.
Go farther and use stop U.S. 64, and everything
from about five feet and one-quarter to about seven-
teen feet will be sharp.
It will'thus be seen that the smaller the stop the
greater the depth of focus, that is, the greater the
power of the lens to define sharply, at the same
time, objects nearer the camera and farther from
the camera than the principal object in the picture,
which, of course, is the object focused upon. But
it is obvious that with the small stops the exposure
must be correspondingly increased.
The following table will be a help in finding
the range of sharp definition or depth of focus when
the No. 2-A Folding Autographic Brownie Camera
(when it is fitted with the Rapid Rectilinear Lens)
is focused with different stops:
u.s.
4 u.s.8 u.s.
16 u.s.32 u.s.64
u.s.4
u.s,g
u.s.
16
u.s.32
u.s.64
COPYRIGHT 1922, gY EASTMAN KODAK CO.
Diaphragms
The diaphragms, sometimes called stops, should
be used as follows:
U.S. 4-For instantaneous exposures
on slightly cloudy days,
use speed 25; also for portraits out of doors, when the sun
is shining,see
page 14.
U.S. 8-For ordinary outdoor work, such as street scenes,
nearby views, etc., when the subject is in bright sunshine,
usespeed
25.
U.S. 16-For open views, etc., when the sunlight on the
subject is unusually strong and there are no heavy shad-ows,
such as views at the seashore,and on the water, use speed 50;
for ordinary landscapes, in bright sunshine, rvith clear sky
overhead, use speed 25; also for Interior Time Exposures,
the time for which is given in the table on pages 32 and 33.
U.S. 32-For instantaneous exposures of extremely distant
views. marine. snow scenes and clouds, in bright sunshine,
use speed25; also for Time Exposures.
U.S. 64-For Time Exposures Outdoors in cloudy weather.
Neaerfor instantaneoils ex|osures. The exposure required for
time exposures on cloudy days with smallest stop will range
This diagram shows the
actual sizes of the stop
openings or diaphragms of
the shutter used on the
No. 2-A Folding Autogra-
phic Brownie, when the
camera is fitted with the
Rapid Rectilinear Lens.
It clearly shows the rel-
ative sizes of the various
stop openings and the
difference between their
areas.
.l
V
o
o
o
o
4I
J
Distance I
Focused I
Upon .l RANGE OF SHARPNESS
Ft. Ft. Ft. Ft. Ft. Ft. Ft. Ft. Ft. Ft.
"Inf." is the abbreviation for Infinity-meaning an infini
distance from the lens.
to Inf.l2l to Inf. I
17to Inf.l 12to
%to68 lll% to Inf. |
|| to Inf.l 9 to
ro9%l 6% to lo%l 6 to 13 l5/a to
5
I
to Inf. |
2
to46 ll
ro9%|
100
Ft. 135
25Ft. lt7
%
8Ft. | 7% {
Inf
Inf
t7
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16 t7